Electrical relay



A. E DODD ELEQTRICAL RELAY Filed Aug. 31, 1943 TI s img/ 2 Sheets-Sheet l :ETV::Illrh BY 'Qi www@ HIJ ATTORNEY @Qil, 1945. A. @QED ELECTR CAL RELAY Filed Aug. 31, 1945 2 sheets-sheet 2 INVNTOR Patented Oct. 16, 1945 UNITED STATES PATENT OFFICE ELECTRICAL RELAY Arthur E. Dodd, Edgewood, Pa., assignor to The Union Switch & Signal Company, Swssvale, Pa., a corporation of Pennsylvania Application August 31, 1943,v Serial No. 500,633

9 Claims.

My invention relates to electrical relays, and particularly to electrical relays having a low resistance conducting path associated therewith for controlling the time characteristics of the relay.

Relays of the type described exhibit the characteristic that the release time decreases with increases in the ambient temperature. This change in the time characteristics of the relay is undesirabley and one object ci my invention is the provision of means for automatically compensating for' the effects of changes in the ambient temperature upon the time characteristics of a relay of the type described.

Relays embodying my invention are an improvement upon the relay described and claimed in Letters Patent of the United States No. 1,716,808, granted to Herbert A. Wallace on June 1l, 1929, for Electromagnetic device.

I shall describe two forms of electrical relays embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a side elevational View with some of the parts in section of a relay provided with one form of temperature compensating means embodying my invention. Fig. 2 isa back view of the relay shown in Fig. l, with certain of the parts shown in section. Fig. 3 is a side View showing a relay similar to that illustrated in Fig. l provided with another form of temperature compensating means embodying my invention.

Similar vreference characters refer to similar parts in all three views.

Referring nrst to Figs. l and 2, the relay here shown Acomprises a top plate I of suitable insulating 'material such as a phenol condensation product, which 'top plate supports all of the operating parts of the relay. Mounted on` the top plate I is an electromagnet A comprising, as usual, a pair of parallel cores 2 and 2a connected at their upper ends by a backstrap 3, and provided at their lower ends with enlarged pole pieces 4 and 4a disposed on the underside of the top plate. The cores 2 and 2a are surrounded by energizing windings 5 and 5a wound on sleeves 6 and 6a, respectively, of low resistance conducting material. The sleeves 6 and 6a comprise a means for controlling the time constants of the relay as will be made clear presently. The windings 5 and 5a are vintended to be connected in series in the usual manner so as to provide cumulative fluxes in the cores 2 and 2a when these windings are energized., and may be supplied with current from any suitable source not shown in the drawings.

The relay also comprises the usual tractive anmature 'I which is pivotally supported for movement toward and away from the pole pieces 4 and 4a according as the windings 5 and 5a are energized ordeenergzed. The movement of the armature toward the pole pieces is limited by the usual is swung away from the pole pieces.

non-magnetic core pins 1a. Attached to the armature by means of insulating supports 8 are a plurality oi ilexible contact lingers 9. Each contact nger 9 cooperates with a xed front contact member 9a to close a front contact 9--9a when the armature is swung toward the pole pieces, and with a xed back contact member 9b to close a back Contact 9-9b when the armature Each fixed front contact member 9a is secured to a terminal post I il mounted on the top plate I, while each Xed contact member 9b is secured to a terminal post I I also mounted on the top plate I.

. External electrical contact with each movable contact finger 9 is made through the medilm'i of a flexible connector I2 connected to a terminal post I3 mounted on the top plate I.

With the relay constructed in the manner thus l far described it will be obvious that when the electromagnet Abecomes energized, the armature 8 will move Itoward the pole pieces 4 and 4a to its attracted position in which the core pins 'Ia engage the pole pieces, and will thus close the front contacts 9--9a. When the electromagnet 3 subsequently becomes deenergized, the electromotive Vforces induced in sleeves 6 and 6a will delay the decay of the flux in the cores I and Ia, and as a result, the release of the armature will be delayed. However, as soon as the flux in the cores drops below the critical value, the armature will then drop by gravity to its released position and will thus open the front contacts 9-9a and close the back contacts 9-9b. It will be seen,

Y therefore. that due to the slow acting sleeves 6 and 6a the release of the armature l will occur at the expiration of a predetermined time interval after the relay becomes deenergized.

The time required for the armature I to release depends .in part upon the degree to which the electromagnet was previously energized, and in part upon the resistance of the slow acting sleeves 5 and 6a. If the ambient temperature increases, the resistance of the energizing windings will increase, and assuming that the relay is energized from a source of constant potential, the energization of the electromagnet will then decrease With the result that the release time of the armature will decrease. Furthermore, if the sleeves 6 and 6a are made of a material such as copper whichhas a positive temperature coeficient of resistance, a rise in the ambient temperature will increase the resistance of these sleeves 4so that for a given energizing current in the windings A5 and 5a the current induced in the sleeves 6 and 6a will be materially lessened. The .smaller the induced current in sleeves 6 and 6a becomes the quicker the flux induced in the cores 2 and 2a will decrease to the level at which the armature releases after the windings 5 and 5a become deenergized, and it follows, therefore,

that increases in the ambient temperature will decrease the effectiveness of the sleeves and will thus act to accelerate the 'release of the relay. The accelerationof the release time of the relay due to theincrease in resistance f the sleevesV is rather large, and in actual practice the combined effect of the change in resistance of the windings and the sleeves may cause the release time at the highest temperature to which the relays may be subjected to be less than half of the release time a-t the lowest temperature'to which the relays may be subjected.

It is frequently desirable to employ a relay of the type described where a constant rate 0f release is necessary, and according to my present invention I provide the relay with temperature compensating means which I shall now describe forA rendering the time characteristics of the relay independent of changes in the ambient temperature.

` As shown in Figs, 1 and 2, the temperature compensating means comprises two temperature compensators TI and T2 which vserve to Vary the air gap at the back of the armature in response to temperature changes, and also to vary the position of a magnetic shunt with respect to the polepieces Il and lla. These compensators are disposed adjacent the rear edge of the relay on opposite sides of the operating windings, and each comprises Aa tube i5 of a material having a high temperature coefficient of linear expansion, such asr aluminum or brass, and a rod i6 of a material having a relatively low temperature coemcient of linear expansion, such as porcelain or invar. The tubes I5 are screw threaded at their lower ends into through holes I'I provided in the top plate I, and each tube is internally threaded at its upper end for threaded engagement with an enlarged portion Ia provided on the upper end of the associated rod I5. The rods IS extend downwardly through the tubes I5 with clearance and are provided at their lower ends with brackets I8 carrying trunnion screws I9 which pivotally support the armature The rods I6 also support a shunt bar 2U which extends transversely ofthe relay above polar extensions @il and @ila provided on the polepieces i and 4a respectively. The brackets I8 and shunt bar Eil are secured to the lower ends of the rods Iii by means of screws 2l which pass through clearance holes in the brackets and the shunt bar and are screwed into tapped holes I6b provided in the rods.

With the temperature compensating means constructed in this manner a rise in the ambient temperature will cause the metal tubes I5 to elongate an appreciable amount While the rods l will elongate only a very slight amount, if any. The resultant relative motion between the tubes and rods causes the air gaps between the pole pieces and the armature to decrease, thereby decreasing the reluctance of the air gaps, and hence increasing the magnitude of the working flux traversing the armature. This relative motion between the tubes and rods also causes the air gaps between the shunt bar and the polar extensions to increase, which decreases the leakage flux through the shunt bar and hence further increases the Working 'ux traversing the armature. In a similar manner, a decrease in the ambient temperature will cause the air gaps between the armature and the pole piece to increase and the air gaps between the shunt bar and the polar extension to decrease which causes a decrease in the working flux traversing the armature. As was pointed out hereinbefore, any increase in the ambient temperature without the temperature compensating means tends to decrease the flux traversing the armature, and it follows therefore that by properly proportioning the parts the temperature compensators can be made to maintain the iluX traversing the armature at a value which maintains the release time substantially constant. It also follows that the parts can be so proportioned as to cause the temperature compensating means to overcompensate or undercompensate for changes in the release time of the relay caused by changes in the ambient temperature.

It should be pointed out that while the relay as constructed in Figs. l and 2. makes use of both changes in the armature air gaps and a magnetic shunt bar to obtain temperature compensation, each-of these meansl may be used independently, if desired.

Referring now to Fig. 3, in the modified form of my invention here shown, the relay is provided with only one temperature compensator T3. This latter Vtemperature 'compensator` is mounted in a screw threaded rhole 22 provided i in the top plate I directly in front of windings' and 5a on a line midway between them, and is similar to the previously describedtemperature compensators TI and T2 except for the fact thatthe inner rod, which latter lrod is here designated 23, is provided at Vits lower end with a gap between the pole pieces 4 and da and armature 'I to decrease. This decreaseV in air gap causes a greater amount of the magnetic ux induced in the electromagnet by the energizetion of the windings o and 5a to traverse Vthe armature, and by properly. proportioning the parts the increase in iiux traversing the armature caused by the change in air gap canbe made suflicient to result in the Vrelease time of the relay being maintained substantially constant.

If desired the temperature compensator T3 can be combined with the temperature compensators TIV and T2 shown in Fig. 1.

One advantage of. temperature compensating means embodying my invention is that it is rugged and reliable, aswell as being relatively inexpensive to manufacture. Y n Although I have herein shown and described only two` forms of electrical relays embodying my invention, it is understood that variousrchang'es and modifications may be made therein within the scope of the appended Aclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is: 1

1. In combination, an electromagnet-provided with pole pieces, an armature controlled by said electromagnet, a magnetizable shunting member spaced from each pole piece of said electromagnet by an air gap, and means for-varying said air gaps in response to changes inl the ambient temperature to compensate for changes in the time constants of said relay caused by said ambient temperature changes comprising a tube iixed at one end, and a rod secured at one end within the free end of said tube and extending through said tube with clearance and secured at its free end to said shunting member, said tube and said rod having diierent coeiiicients of linear expansion.

2. In combination, an electromagnet provided With pole pieces, an armature controlled by said electromagnety a magnetizable shunting member spaced from each pole piece of said electromagnet by an air gap, and means for varying said air gap in response to changes in the ambient temperature to compensate for changes in the time constants of said relay caused by said ambient temperature changes comprising a tube fixed at one end, and a rod secured at one end within the free end of said tube and extending through said tube with clearance and secured at its free end to said shunting member, said tube having a relatively high coeiiicient of linear expansion and said rod having a relatively lovi7 coeiiicient of linear expansion.

3. In combination, an electromagnet provided with pole pieces, an armature controlled by said electromagnet, a magnetizable shunting member spaced from each pole piece of said electromagnet by an air gap, and means for varying said air gaps in response to changes in the ambient temperature to control the changes in the time constants of said relay caused by said ambient temperature changes comprising a tube fixed at one end, and a rod secured at one end within the free end of said tube and extending through said tube with clearance and secured at its free end to said shunting member, said tube and said rod having diierent coefcients of linear expansion.

4. In combination, an electromagnet provided With pole pieces and with a low resistance conducting path for controlling the time constants of said magnet, an armature' controlled by said electromagnet, a magnetizable shunting member spaced from each pole piece of said electromagnet by an air gap, and means for varying said air gaps in response to changes in the ambient temperature to compensate for changes in the time constants of said relay caused by said ambient temperature changes comprising a tube xed at one end, and a rod secured at one end Within the free end of said tube and extending through said tube with clearance and secured at its free end to said shunting member, said tube and said rod having different coeiiicients of linear expansion.

5. An electrical relay comprising an electromagnet provided with a pair of pole pieces, an armature cooperating with said electromagnet, a pair of temperature compensators each comprising a tube xed at one end and a rod extending into said tube through said one end and secured to the other end of said tube, said tube and said rod having different coeflicients of linear expansion, supports for said armature secured to the free ends of said rods, and a shunt bar secured to the free ends of said rods and separated from said pole pieces by air gaps which depend upon the relative lengths of said tubes and said rods, said tubes and said rods having diierent coeicients of linear expansion.

6. An electrical relay comprising an electromagnet provided with a pair of pole pieces, an armature cooperating with said electromagnet, a pair of temperature compensators each comprising a tube fixed at one end and a rod extending into said tube through said one end and secured to the other end of said tube, said tube and said rod having different coefficients of linear expansion, supports for said armature secured to the free ends of said rods, and a shunt bar secured to the free ends of said rods and separated from said pole pieces by air gaps which depend upon the relative lengths of said tubes and said rods, said tubes and said rods having diiierent ccedicients of linear expansion so chosen that the changes in the air gaps between said armature and said pole pieces and between said shunt bar and said pole pieces will compensate for changes in the time constants of said relay caused by changes in the ambient temperature.

7. An electrical relay comprising an electromagnet provided with a pair of pole pieces and With a low resistance conducting path for controlling the time constants of said magnet, an armature cooperating with said electromagnet, a pair of temperature compensators each comprising a tube fixed at one end and a rod extending into said tube through said one end and secured to the other end of said tube, said tube and said rod having diierent coefcients of linear expansion, supports for said armature secured to the free ends of said rods, and a shunt bar secured to the free ends of said rods and separated from said pole pieces by air gaps which depend upon the relative lengths of said tubes and said rods, said tubes and said rods having different coefcients of linear expansion.

8. In combination, an electromagnet provided with pole pieces, an armature controlled by said electromagnet, extensions on said pole pieces, two temperature compensators each comprising a tube xed at one end and a rod secured at one end to the other end of said tube and extending through said tube with clearance, and a magnetizable shunt bar secured to the free ends of said rod and spaced from said polar extensions by air gaps, said tubes having different coeiiicients of linear expansion from said rods Whereby variations in the ambient temperature will vary the air gaps between said shunt bar and said polar extensions to control the changes in the time constants of said relay caused by changes in the ambient temperature.

9. In combination, an electromagnet provided with pole pieces and with a slow acting sleeve, an armature controlled by said electromagnet, extensions on said pole pieces, two temperature compensators each comprising a tube fixed at one end and a rod secured at one end to the other end of said tube and extending through said tube with clearance, and a magnetizable shunt bar secured to the free ends of said rod and spaced from said polar extensions by air gaps, said tubes having different coefficients of linear expansion from said rods whereby variations in the ambient temperature will vary the air gaps between said shunt bar and said polar extensions to control the changes in the time constants of said relay caused Iby changes in the ambient temperature.

ARTHUR E. DODD. 

